docs: def update(gandi, address, dest_add, dest_del):
      """Update a domain mail forward."""
      source, domain = address
  
      if not dest_add and not dest_del:
          gandi.echo('Nothing to update: you must provide destinations to '
                     'update, use --dest-add/-a or -dest-del/-d parameters.')
          return
  
      result = gandi.forward.update(domain, source, dest_add, dest_del)
  
      return result